1. Field of the Invention
The present invention relates to a data processing apparatus which can take a standby state in which a job can be executed, and a suspended state serving as a power saving state, and a control method therefor.
2. Description of the Related Art
Recently, image forming apparatuses which have a power saving mode are becoming popular. An image forming apparatus of this type implements the power saving mode by reducing (or shutting down) the power supply to a main control unit, which controls the image forming apparatus when the image forming apparatus shifts to a non-standby state, from a normal state.
Also, recent image forming apparatuses include an auxiliary storage device (for example, a hard disk) as standard equipment. The auxiliary storage device can hold user data, and save temporary data to be used when forming an image, or to be used in each processing to be executed by the image forming apparatus.
Under the circumstances, a demand has arisen for an image forming apparatus capable of quickly shifting from a power saving state to a power-off state by a combination of the power saving mode and an auxiliary storage device. Another demand has also arisen for an image forming apparatus capable of quickly shifting to a standby state after power-on again, after shifting from a power saving state to a power-off state. For example, in Japanese Patent Laid-Open No. 11-194846, when a battery-driven information processing apparatus shifts to a low-battery state during a sleep operation, it temporarily returns to the standby state, and executes a hibernation operation to create a hibernation image and save it in an auxiliary storage device.
In the technique disclosed in Japanese Patent Laid-Open No. 11-194846, when power supply from an internal battery or external power source stops during the suspension period, the BIOS is notified of this as a wakeup event. After the contents of the memory are saved in a hibernation area within the hard disk, the information processing apparatus is turned off. In this manner, the system state shifts from the suspended state to the hibernation state, thereby controlling the system state so as not to lose information even in a low-battery state.
In the technique disclosed in Japanese Patent Laid-Open No. 11-194846, when the user turns off the image forming apparatus in the suspended state, the system state temporarily returns from the suspended state to the standby state, and then the image forming apparatus is turned off. Hence, when the image forming apparatus in the suspended state shifts to the power-off state, it temporarily returns to the standby state and thus takes time, compared to directly shifting from the suspended state to the power-off state.
In general, when the user performs an operation to turn off the image forming apparatus, he may think that power-off has been completed by this operation. In some cases, the user may remove the power cord from the outlet during shutdown processing. If the power cord is removed during shutdown processing, a logical fault may occur in the auxiliary storage device.
When the user performs an operation to turn off the image forming apparatus in the suspended state, the image forming apparatus can stop power supply and quickly shift to the power-off state without performing shutdown processing. In this case, however, upon power-on at a later time, the image forming apparatus is activated while executing an inconsistency check, because flush processing for various caches that should be executed during shutdown processing has not been performed. For this reason, the time taken to shift from the power-off state to the standby state becomes very long.